Thin-film transistor and semiconductor device using thin-film transistors

Abstract

In those thin-film transistors (TFTs) employing as its active layer a silicon film crystallized using a metal element, the objective is to eliminate bad affection of such metal element to the TFT characteristics. To this end, in a TFT having as its active layer a crystalline silicon film that was crystallized using nickel (Ni), those regions corresponding to the source/drain thereof are doped with phosphorus; thereafter, thermal processing is performed. During this process, nickel residing in a channel formation region is “gettered” into previously phosphorus-doped regions. With such an arrangement, it becomes possible to reduce the Ni concentration in certain regions in which lightly-doped impurity regions will be formed later, which in turn enables suppression of affection to TFT characteristics.

What is claimed is:  
     
       1. An active matrix display device comprising: 
       an active matrix circuit and a driving circuit formed over a substrate;  
       at least one thin film transistor formed in said active matrix circuit, said thin film transistor comprising:  
       a semiconductor film formed on an insulating surface;  
       a channel region formed in said semiconductor film;  
       a pair of impurity regions formed in said semiconductor film; and  
       a region formed between said channel region and one of said pair of impurity regions,  
       wherein said pair of impurity regions contains an n-type impurity element at a concentration higher than in said region,  
       wherein said pair of impurity regions contains a metal element for acceleration of crystallization of silicon at a concentration higher than said region.  
     
     
       2. An active matrix display device according to  claim 1 , wherein said n-type impurity element is phosphorus. 
     
     
       3. An active matrix display device according to  claim 1 , wherein said metal element is selected from the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu and Au. 
     
     
       4. An active matrix display device according to  claim 1 , wherein said active matrix display device is incorporated into an electronic equipment selected from the group consisting of a portable computer, a head mount display, a portable phone, a video camera, a front-type projector and a rear-type projector. 
     
     
       5. An active matrix display device comprising: 
       an active matrix circuit and a driving circuit formed over a substrate;  
       at least one thin film transistor formed in said driving circuit, said thin film transistor comprising:  
       a semiconductor film formed on an insulating surface;  
       a channel region formed in said semiconductor film;  
       a pair of impurity regions formed in said semiconductor film; and  
       a region formed between said channel region and one of said pair of impurity regions,  
       wherein said pair of impurity regions contains an n-type impurity element at a concentration higher than in said region,  
       wherein said pair of impurity regions contains a metal element for acceleration of crystallization of silicon at a concentration higher than said region.  
     
     
       6. An active matrix display device according to  claim 5 , wherein said n-type impurity element is phosphorus. 
     
     
       7. An active matrix display device according to  claim 5 , wherein said metal element is selected from the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu and Au. 
     
     
       8. An active matrix display device according to  claim 5 , wherein said active matrix display device is incorporated into an electronic equipment selected from the group consisting of a portable computer, a head mount display, a portable phone, a video camera, a front-type projector and a rear-type projector. 
     
     
       9. An active matrix display device comprising: 
       an active matrix circuit and a driving circuit formed over a substrate;  
       at least one thin film transistor formed in said driving circuit, said thin film transistor comprising:  
       a semiconductor film formed on an insulating surface;  
       a channel region formed in said semiconductor film;  
       a pair of impurity regions formed in said semiconductor film; and  
       a region formed between said channel region and one of said pair of impurity regions,  
       wherein said pair of impurity regions contains an n-type and a p-type impurity elements,  
       wherein a concentration of said n-type impurity element in said pair of impurity regions is higher than that in said region,  
       wherein said pair of impurity regions contains a metal element for acceleration of crystallization of silicon at a concentration higher than said region.  
     
     
       10. An active matrix display device according to  claim 9 , wherein said n-type impurity element is phosphorus and said p-type impurity element is boron. 
     
     
       11. An active matrix display device according to  claim 9 , wherein said metal element is selected from the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu and Au. 
     
     
       12. An active matrix display device according to  claim 9 , wherein said active matrix display device is incorporated into an electronic equipment selected from the group consisting of a portable computer, a head mount display, a portable phone, a video camera, a front-type projector and a rear-type projector. 
     
     
       13. An EL display device comprising: 
       an active matrix circuit and a driving circuit formed over a substrate;  
       at least one thin film transistor formed in each of said active matrix circuit and said driving circuit, said thin film transistor comprising:  
       a semiconductor film formed on an insulating surface;  
       a channel region formed in said semiconductor film;  
       a pair of impurity regions formed in said semiconductor film; and  
       a region formed between said channel region and one of said pair of impurity regions,  
       wherein said pair of impurity regions contains an n-type impurity element at a concentration higher than said region,  
       wherein said pair of impurity regions contains a metal element for acceleration of crystallization of silicon at a concentration higher than said region.  
     
     
       14. An EL display device according to  claim 13 , wherein said n-type impurity element is phosphorus. 
     
     
       15. An EL display device according to  claim 13 , wherein said metal element is selected from the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu and Au. 
     
     
       16. An EL display device according to  claim 13 , wherein said EL display device is incorporated into an electronic equipment selected from the group consisting of a portable computer, a head mount display, a portable phone, a video camera, a front-type projector and a rear-type projector. 
     
     
       17. An EL display device comprising: 
       an active matrix circuit and a driving circuit formed over a substrate;  
       at least one thin film transistor formed in said active matrix circuit and said driving circuit, said thin film transistor comprising:  
       a semiconductor film formed on an insulating surface;  
       a channel region formed in said semiconductor film;  
       a pair of impurity regions formed in said semiconductor film; and  
       a region formed between said channel region and one of said pair of impurity regions,  
       wherein said pair of impurity regions contains an n-type impurity element at a concentration higher than in said region,  
       wherein said pair of impurity regions contains a metal element for acceleration of crystallization of silicon at a concentration higher than said region.  
     
     
       18. An EL display device according to  claim 17 , wherein said n-type impurity element is phosphorus. 
     
     
       19. An EL display device according to  claim 17 , wherein said metal element is selected from the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu and Au. 
     
     
       20. An EL display device according to  claim 17 , wherein said EL display device is incorporated into an electronic equipment selected from the group consisting of a portable computer, a head mount display, a portable phone, a video camera, a front-type projector and a rear-type projector. 
     
     
       21. An EL display device comprising: 
       an active matrix circuit and a driving circuit formed over a substrate;  
       at least one thin film transistor formed in said active matrix circuit and said driving circuit, said thin film transistor comprising:  
       a semiconductor film formed on an insulating surface;  
       a channel region formed in said semiconductor film;  
       a pair of impurity regions formed in said semiconductor film; and  
       a region formed between said channel region and one of said pair of impurity regions,  
       wherein said pair of impurity regions contains an n-type and a p-type impurity elements,  
       wherein a concentration of said n-type impurity element in said pair of impurity region is higher than that in said region,  
       wherein said pair of impurity regions contains a metal element for acceleration of crystallization of silicon at a concentration higher than said region.  
     
     
       22. An EL display device according to  claim 21 , wherein said n-type impurity is phosphorus and p-type impurity element is boron. 
     
     
       23. An EL display device according to  claim 21 , wherein said metal element is selected from the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Cu and Au. 
     
     
       24. An EL display device according to  claim 21 , wherein said EL display device is incorporated into an electronic equipment selected from the group consisting of a portable computer, a head mount display, a portable phone, a video camera, a front-type projector and a rear-type projector.